Allogeneic bone marrow transplantation (BMT) is associated with prolonged periods of neutropenia and thrombocytopenia, which can lead to severe infections and bleeding complications. Transplantation-related side effects might be ameliorated by use of cytokine-mobilized peripheral blood progenitor cells (PBPC) instead of bone marrow. We have studied PBPC mobilization and transplantation in more than 150 patients with high-risk hematologic malignancies. Normal donors can be sufficiently mobilized with granulocyte colony-stimulating factor (G-CSF), with 91% of G-CSF-stimulated normal donors producing more than 2 x 106 CD34+ cells/kg by a single apheresis. The combination of G-CSF plus granulocyte-macrophage colony- stimulating factor (GM-CSF) was more effective than mobilization with G-CSF alone. A clear relationship was seen between numbers of resting CD34+ cells premobilization and numbers of PBPC collected by apheresis, indicating that resting CD34+ cells might be used to predict mobilization results and identify donors who could benefit from more effective mobilization regimens. Transplantation of G-CSF-mobilized PBPC was associated with a more rapid engraftment than that observed for BMT. While engraftment was safe and acute graft-versus-host disease (aGvHD) rates were not increased over BMT, chronic GvHD rates were higher after PBPC transplantation. An additional PBPC infusion on day +3 resulted in a further shortening of neutropenia and thrombocytopenia. Incorporation of these innovative approaches with 'minimal' conditioning regimens has resulted in near-complete elimination of fever, neutropenia, thrombocytopenia, and the need for antibiotics and RBC and platelet transfusions after allogeneic transplantation. Copyright (C) 2000 by W.B. Saunders Company.